/*
 * $Id: FastBlurFilter.java 4082 2011-11-15 18:39:43Z kschaefe $
 *
 * Dual-licensed under LGPL (Sun and Romain Guy) and BSD (Romain Guy).
 *
 * Copyright 2006 Sun Microsystems, Inc., 4150 Network Circle,
 * Santa Clara, California 95054, U.S.A. All rights reserved.
 *
 * Copyright (c) 2006 Romain Guy <romain.guy@mac.com>
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. The name of the author may not be used to endorse or promote products
 *    derived from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

package org.jdesktop.swingx.image;

import java.awt.image.BufferedImage;

import org.jdesktop.swingx.util.GraphicsUtilities;

/**
 * <p>
 * A fast blur filter can be used to blur pictures quickly. This filter is an
 * implementation of the box blur algorithm. The blurs generated by this
 * algorithm might show square artifacts, especially on pictures containing
 * straight lines (rectangles, text, etc.) On most pictures though, the result
 * will look very good.
 * </p>
 * <p>
 * The force of the blur can be controlled with a radius and the default radius
 * is 3. Since the blur clamps values on the edges of the source picture, you
 * might need to provide a picture with empty borders to avoid artifacts at the
 * edges. The performance of this filter are independent from the radius.
 * </p>
 *
 * @author Romain Guy <romain.guy@mac.com>
 */
public class FastBlurFilter extends AbstractFilter {
	private final int radius;

	/**
	 * <p>
	 * Creates a new blur filter with a default radius of 3.
	 * </p>
	 */
	public FastBlurFilter() {
		this(3);
	}

	/**
	 * <p>
	 * Creates a new blur filter with the specified radius. If the radius is
	 * lower than 1, a radius of 1 will be used automatically.
	 * </p>
	 *
	 * @param radius
	 *            the radius, in pixels, of the blur
	 */
	public FastBlurFilter(int radius) {
		if (radius < 1) {
			radius = 1;
		}

		this.radius = radius;
	}

	/**
	 * <p>
	 * Returns the radius used by this filter, in pixels.
	 * </p>
	 *
	 * @return the radius of the blur
	 */
	public int getRadius() {
		return radius;
	}

	/**
	 * {@inheritDoc}
	 */
	@Override
	public BufferedImage filter(BufferedImage src, BufferedImage dst) {
		int width = src.getWidth();
		int height = src.getHeight();

		if (dst == null) {
			dst = createCompatibleDestImage(src, null);
		}

		int[] srcPixels = new int[width * height];
		int[] dstPixels = new int[width * height];

		GraphicsUtilities.getPixels(src, 0, 0, width, height, srcPixels);
		// horizontal pass
		blur(srcPixels, dstPixels, width, height, radius);
		// vertical pass
		// noinspection SuspiciousNameCombination
		blur(dstPixels, srcPixels, height, width, radius);
		// the result is now stored in srcPixels due to the 2nd pass
		GraphicsUtilities.setPixels(dst, 0, 0, width, height, srcPixels);

		return dst;
	}

	/**
	 * <p>
	 * Blurs the source pixels into the destination pixels. The force of the
	 * blur is specified by the radius which must be greater than 0.
	 * </p>
	 * <p>
	 * The source and destination pixels arrays are expected to be in the
	 * INT_ARGB format.
	 * </p>
	 * <p>
	 * After this method is executed, dstPixels contains a transposed and
	 * filtered copy of srcPixels.
	 * </p>
	 *
	 * @param srcPixels
	 *            the source pixels
	 * @param dstPixels
	 *            the destination pixels
	 * @param width
	 *            the width of the source picture
	 * @param height
	 *            the height of the source picture
	 * @param radius
	 *            the radius of the blur effect
	 */
	static void blur(int[] srcPixels, int[] dstPixels, int width, int height, int radius) {
		final int windowSize = radius * 2 + 1;
		final int radiusPlusOne = radius + 1;

		int sumAlpha;
		int sumRed;
		int sumGreen;
		int sumBlue;

		int srcIndex = 0;
		int dstIndex;
		int pixel;

		int[] sumLookupTable = new int[256 * windowSize];
		for (int i = 0; i < sumLookupTable.length; i++) {
			sumLookupTable[i] = i / windowSize;
		}

		int[] indexLookupTable = new int[radiusPlusOne];
		if (radius < width) {
			for (int i = 0; i < indexLookupTable.length; i++) {
				indexLookupTable[i] = i;
			}
		} else {
			for (int i = 0; i < width; i++) {
				indexLookupTable[i] = i;
			}
			for (int i = width; i < indexLookupTable.length; i++) {
				indexLookupTable[i] = width - 1;
			}
		}

		for (int y = 0; y < height; y++) {
			sumAlpha = sumRed = sumGreen = sumBlue = 0;
			dstIndex = y;

			pixel = srcPixels[srcIndex];
			sumAlpha += radiusPlusOne * ((pixel >> 24) & 0xFF);
			sumRed += radiusPlusOne * ((pixel >> 16) & 0xFF);
			sumGreen += radiusPlusOne * ((pixel >> 8) & 0xFF);
			sumBlue += radiusPlusOne * (pixel & 0xFF);

			for (int i = 1; i <= radius; i++) {
				pixel = srcPixels[srcIndex + indexLookupTable[i]];
				sumAlpha += (pixel >> 24) & 0xFF;
				sumRed += (pixel >> 16) & 0xFF;
				sumGreen += (pixel >> 8) & 0xFF;
				sumBlue += pixel & 0xFF;
			}

			for (int x = 0; x < width; x++) {
				dstPixels[dstIndex] = sumLookupTable[sumAlpha] << 24 | sumLookupTable[sumRed] << 16
						| sumLookupTable[sumGreen] << 8 | sumLookupTable[sumBlue];
				dstIndex += height;

				int nextPixelIndex = x + radiusPlusOne;
				if (nextPixelIndex >= width) {
					nextPixelIndex = width - 1;
				}

				int previousPixelIndex = x - radius;
				if (previousPixelIndex < 0) {
					previousPixelIndex = 0;
				}

				int nextPixel = srcPixels[srcIndex + nextPixelIndex];
				int previousPixel = srcPixels[srcIndex + previousPixelIndex];

				sumAlpha += (nextPixel >> 24) & 0xFF;
				sumAlpha -= (previousPixel >> 24) & 0xFF;

				sumRed += (nextPixel >> 16) & 0xFF;
				sumRed -= (previousPixel >> 16) & 0xFF;

				sumGreen += (nextPixel >> 8) & 0xFF;
				sumGreen -= (previousPixel >> 8) & 0xFF;

				sumBlue += nextPixel & 0xFF;
				sumBlue -= previousPixel & 0xFF;
			}

			srcIndex += width;
		}
	}
}
